Utilization of Seawater for Pineapple Cultivation

Abstract

Pineapple needs a large amount of potassium (350 kg K ha-1), which is higher than
the other nutrient requirements. As a crassulacean acid metabolism species, it also
requires some amount of Na as a beneficial nutrient to replace part of potassium’s
function. This provides an opportunity to decrease K fertilizer cost, especially for
non-K fertilizer producer countries such as Malaysia where the import bill for K
fertilizer is the highest compared to N and P fertilizers. A readily available source of
Na is seawater, which contains about 4,000-10,000 mg L-1 Na. Three experiments
were conducted to study the possibility of utilizing nutrients from seawater. The first
experiment was to observe sorption and desorption of K, Na, Ca and Mg from
different concentrations of seawater in natural zeolite. The second and third
experiments were to study the extent to which Na could replace the function of K in
pineapple. The results indicated that natural zeolite could sorb Na, Mg and K from seawater. The highest sorption for Na, Mg and K was from 40% diluted seawater at
2260.00, 210.00 and 60.00 4g g-1 zeolite, respectively. The cations were then
desorbed from zeolite cavities. As a slow release agent of cations, zeolite treated with
20% seawater released 576.67 and 102.33 4g g-1 zeolite of Na and Mg, respectively.
Application of Na for K substitution (0, 15, 30 and 60%) from seawater and NaCl in a
Bungor Series of Typic Paleudult soil resulted in no significant increase in soil pH,
CEC, EC and turbidity. Sodium uptake in D-leaf increased significantly up to 30%
Na for K substitution (diluted seawater) and 60% Na for K substitution (NaCl)
without any toxic effect to the plant. The highest plant dry weight (3.45 kg) was
obtained from 30% Na for K substitution using diluted seawater. However, there was
no significant difference among all treatments for fresh fruit weight. Similar results in
soil properties and Na uptake were also found in a more detailed study conducted in a
Seremban Series of Plintic Kandiudult soil. Application of diluted seawater, NaCl,
and seawater-zeolite effluent decreased plant dry weight which can be attributed to
decreasing cell membrane stability as an indication of toxicity due to increasing Na in
plant tissue for 60% Na for K substitution. However, sodium application induces
thicker water storage tissue in D-leaf, which may be an adaptation response of
pineapple to increased Na. In general, the results of the study indicated that zeolite
can sorb and desorb Na, Mg and K; and 30% of pineapple K requirement (in term of
fertilizer application) can be replaced by Na from diluted seawater, NaCl, zeolite
saturated with seawater and seawater-zeolite effluent, and the rest (70%) from K
fertilizer.